merkle
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Javascript implementation of merkle trees
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# Merkle [](https://travis-ci.org/c-geek/merkle) [](http://badge.fury.io/js/merkle) [](https://github.com/c-geek/merkle/blob/master/LICENSE)
Builds a Merkle tree using either sha512, sha256, ripemd160, whirlpool, sha1, md5 or none algorithms.
## Usage
### Build a Merkle tree
```js
var merkle = require('merkle');
var abcde = ['a', 'b', 'c', 'd', 'e'];
```
#### Sync style
```js
var tree = merkle('sha1').sync(abcde);
```
#### Async style
```js
merkle('sha1').async(abcde, function(err, tree){
// ...
});
```
#### Stream style
```js
// Stream style -- streams root hash
var merkleStreamRoot = merkle('sha1');
merkleStreamRoot.pipe(process.stdout);
// Stream style -- streams json tree
var es = require('event-stream');
var merkleStreamJson = merkle('sha1').json();
merkleStreamJson
.pipe(es.stringify())
.pipe(process.stdout);
abcde.forEach(function(letter){
merkleStreamJson.write(letter);
});
merkleStreamJson.end();
// out:
// {"root":"114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9","depth":3,"levels":4,"nodes":6}
```
### Extract tree data
You can get tree root using:
```js
> tree.root();
'114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9'
```
Get tree depth:
```js
> tree.depth();
3
```
Get tree number of levels (depth + level of leaves):
```js
> tree.levels();
4
```
Get tree number of nodes
```js
> tree.nodes();
6
```
Get a tree level nodes:
```js
> tree.level(0);
['114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9']
> tree.level(1);
[
'585DD1B0A3A55D9A36DE747EC37524D318E2EBEE',
'58E6B3A414A1E090DFC6029ADD0F3555CCBA127F'
]
> tree.level(2);
[
'F4D9EEA3797499E52CC2561F722F935F10365E40',
'734F7A56211B581395CB40129D307A0717538088',
'58E6B3A414A1E090DFC6029ADD0F3555CCBA127F'
]
...
```
### Using different hash algorithms
```js
var sha256tree= merkle('sha256').sync(abcde);
var sha1tree = merkle('sha1').sync(abcde);
var md5tree = merkle('md5').sync(abcde);
var cleartree = merkle('none').sync(abcde);
> sha256tree.root();
'16E6BEB3E080910740A2923D6091618CAA9968AEAD8A52D187D725D199548E2C'
> sha1tree.root();
'114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9'
> md5tree.root();
'064705BD78652C090975702C9E02E229'
> cleartree.root();
'ABCDE'
```
### Install globally for merkle command
Installing it globally will introduce the `merkle` command (using sha1 as default):
```bash
$ sudo npm install -g merkle
$ merkle a
86F7E437FAA5A7FCE15D1DDCB9EAEAEA377667B8
```
By default, `merkle` returns the root of the merkle tree:
```bash
$ merkle a b c d e
114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9
```
But it can be asked for some level:
```bash
$ merkle a b c d e -l 0
114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9
$ merkle a b c d e -l 1
585DD1B0A3A55D9A36DE747EC37524D318E2EBEE
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F
```
Or even all levels:
```bash
merkle a b c d e --all
114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9
585DD1B0A3A55D9A36DE747EC37524D318E2EBEE
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F
F4D9EEA3797499E52CC2561F722F935F10365E40
734F7A56211B581395CB40129D307A0717538088
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F
86F7E437FAA5A7FCE15D1DDCB9EAEAEA377667B8
E9D71F5EE7C92D6DC9E92FFDAD17B8BD49418F98
84A516841BA77A5B4648DE2CD0DFCB30EA46DBB4
3C363836CF4E16666669A25DA280A1865C2D2874
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F
```
You can also change of hash algorithm:
```bash
$ merkle a b c d e -h md5
064705BD78652C090975702C9E02E229
$ merkle a b c d e -h clear
ABCDE
```
And just extract some computation statistics:
```bash
$ merkle a b c d e --count
4
=> Total number of levels
$ merkle a b c d e --nodes
6
=> Total number of nodes
```
Finally, you can ask for help:
```bash
$ merkle --help
Build a Merkle Tree and prints its values.
Usage: merkle [leaf...]
Options:
--version Prints version
--help Prints help
-l, --level Prints values of the given level. Defaults to 0 (root).
-n, --nodes Prints the number of nodes for the given leaves.
-c, --count Prints the number of levels for the given leaves.
-h, --hash Hash algorithm to apply on leaves. Values are 'sha1', 'md5' or 'none'.
-a, --all Prints all levels of Merkle tree, from leaves to root.
--level [default: 0]
--hash [default: "sha1"]
```
## Concepts
Here is an example of Merkle tree with 5 leaves (taken from [Tree Hash EXchange format (THEX)](http://web.archive.org/web/20080316033726/http://www.open-content.net/specs/draft-jchapweske-thex-02.html)):
ROOT=H(H+E)
/ \
/ \
H=H(F+G) E
/ \ \
/ \ \
F=H(A+B) G=H(C+D) E
/ \ / \ \
/ \ / \ \
A B C D E
Note: H() is some hash function
Where A,B,C,D,E *may* be already hashed data. If not, those leaves are turned into hashed data (using either *sha1*, *md5* or *clear* algorithm).
With such a tree structure, merkle considers the tree has exactly 6 nodes: `[ROOT,H,E,F,G,E]`. For a given level, nodes are just an array.
Adding a `Z` value would alter the `E` branch of the tree:
ROOT'=H(H+E')
/ \
/ \
H=H(F+G) E'
/ \ \
/ \ \
F=H(A+B) G=H(C+D) E'=H(E+Z)
/ \ / \ / \
/ \ / \ / \
A B C D E Z
`ROOT` changed to `ROOT'`, `E` to `E'`, but `H` did not.
# License
This software is provided under [MIT license](https://raw.github.com/c-geek/merkle/master/LICENSE).